The present invention relates to a polarizing lens mainly used for sunglasses and goggles. More particularly, this invention relates to a polarizing lens used for a sunglasses comprising a curved laminate which comprises a polarizing thin layer and supporting layers being made from polycarbonate-resin and formed on both surfaces of the thin layer, while the invention also relates to a method of producing said polarizing lens and an apparatus for executing the production method related thereto.
Conventionally, there are such sunglasses using polarizing lenses as the one shown in FIG. 18 for example. Taking fashionableness into account, the glasses exemplified in FIG. 18 are designed with a slim width. Both ends of a frame 110 are conspicuously curved by way of surrounding both sides of the bearer's face in order that the sunglasses not only functionally deal with front-directional incident light, but also deal with lateral-directional incident light as well. A pair of lenses 111 secured to the frame 110 are respectively formed with spherical surfaces, each having a small radius of curvature proportional to such a conspicuous curve provided for the frame 110.
In order to produce the above-preferred lens 111, initially, a polarizing lens 100 shown in FIG. 19 is produced from a laminate comprising a polarizing thin layer and supporting layers made from polycarbonate-resin and formed on both surfaces of the thin layer, via steps of pressing the laminate by applying a trimming die to form as a rectangular sheet, and curving the rectangular laminate. Next, the produced polarizing lens 100 are cut into the shape of the frame 110 as per dotted-line shown in FIG. 19 and a lens 111 fitting in with the frame 110 are eventually formed.
A pair of polarizing lenses 100 correctly fitting in with the curved sunglasses shown in FIG. 18, have spherical curved surfaces 2, each surface is so formed that curve 2A along the direction X of the polarizing axis and curve 2B along the direction Y being orthogonal to the polarizing axis are respectively 8R. 1R means that radius of curvature is 523 mm, and this numerical value designating degree of curvature "R" is inversely proportional to radius of curvature. Accordingly, the greater the radius of curvature, the gentler is the curve. Conversely, the greater the numerical value designating curvature, the sharper is the curve.
FIG. 20 exemplifies a method of producing a conventional polarizing lens 100 having an 8R.times.8R curved surface 2. In FIG. 20, the reference numeral 101 designates a lower mold having a concave surface 101A corresponding to the 8R.times.8R curved surface 2. The reference numeral 102 designates an upper mold having a convex pressing surface 102A correctly matching the form of the concavity of the surface 101A. The lower mold 101 is secured onto upper and lower supporting bases 104 and 105 and is subject to heating by a heater 103 built in the supporting base 104. The lower mold 101, supporting bases 104 and 105 are respectively provided with air-absorbing holes 10B, 104A, and 105A for sucking up a molded object by operating absorptive force inside of the concavity of the surface 101A of the mold 101. In addition, the reference numeral 106 shown in FIG. 20 designates a fixing member for integrally securing the upper-and-lower supporting bases 104 and 105.
In order to form a lens 100, initially, the lower mold 101 is heated at 143.about.144.degree. C. by operating the heater 103, and then a laminate 3 is horizontally set onto the surface 101A. In order to facilitate curving work, the laminate 3 is preheated by hot air heated at 140.degree. C. for 5 minutes until the laminate 3 itself is heated to 110.degree. C. Next, the upper mold 102 is lowered while operating absorptive force to the concave surface 101A by operating a vacuum unit (not being illustrated), the laminate 3 is curved between the pressing surface 102A of the upper mold 102 and the surface 101A of the lower mold 101. Next, while rising up the upper mold 102 with maintaining the absorption-activated state inside of the concavity of the surface 101A, shape of the molded object is stably formed via thermal treatment at 160.degree. C. for approximately 5 minutes. Consequently, a polarizing lens 100 provided with an 8R.times.8R curved surface 2 is completed. Finally, the completed lens 100 is drawn out of the concave surface 101A of the lower mold 101.
Nevertheless, in the case of the conventional polarizing lens 100 having an 8R.times.8R curved surface 2, substantial difference is generated between the curvature of the front-side supporting layer and the curvature of the backside supporting layer to cause refractive power of light to increase to generate substantial distortion in the lens. When using sunglasses made of the above-cited polarizing lenses 100, bearer's eyes will incur adverse effect. Refractive power of light can be contracted by way of minimizing difference between the curvature of the surface-side supporting layer and the curvature of the back-side supporting layer by restraining curved surface 2 of the polarizing lens 100 to be 6R.times.6R for example. On the other hand, if the curvature of the curved surface 2 were contracted, curve of the lens 111 become gentle to generate difficulty to properly fit in the lens 111 with the frame 110 having a conspicuous curved form as shown in FIG. 18.